Various float-operated gates or barriers have been used to divert, contain or control the flow of liquids in a variety of situations, most quite different from those described above to which the present invention is particularly suitable. Controlling rising water, for example, especially under flood conditions, is particularly important in protecting property. One such device is described in U.S. Pat. No. 4,377,352, issued Mar. 22, 1983 to Goodstein, which describes a self-actuating water containment barrier. The barrier comprises a plurality of stanchions which are mounted for pivotal movement from a normal dormant horizontal position, to an active vertical position. The stanchions are interconnected with water barrier-forming sheeting to form a barrier which can conform to a particular land mass or shoreline. Float members are mounted on the bottom of the outer ends of the stanchions. At low water levels, the float members rest on a shallow body of water or on the ground in a near horizontal position. As the level of the water rises, the float members cause the stanchions to pivot into a vertical position, thereby raising the sheeting to form a water barrier. This water barrier float system is unsuitable for the above described application where cars or human beings must normally pass over the apparatus involved, or where it is desirable that the barrier wall rise into a protective full position before water builds up behind the wall, as in the applications described above. Also, because the float members are near the outer ends of the stanchions, any substantial turbulence in the water can cause the water to spill over the sheeting which terminates a short distance beyond the float members.
U.S. Pat. No. 3,176,469, issued Apr. 6, 1965 to Fowler, describes a control for automatic float-operated gates for protection against overflow conditions in reservoirs as found in dams or canals, applications very different from those above described. The gate control apparatus described in this patent is a masonry construction which houses a mechanism to control the raising and lowering of the gates. The gate control mechanism includes a float attached to a counterweight system attached to the gate over a pulley suspension. As the water level rises in a float well, the buoying up force of the float diminishes the effective weight of the counterweight. The gate opens as the counterweight lowers in its chamber. Likewise, as the water level diminishes, the opposite effect takes place and the weight of the gate acts to lower the gate.
U.S. Pat. No. 4,073,147, issued Feb. 14, 1978 to Nomura, describes a water gate control system for securing water for irrigation or industrial purposes. These are also applications very different from those to which the present invention is most useful. This patent describes the use of a hydraulic cylinder for controlling the swinging motion of the gate, the cylinder having a piston loaded so as to resist the hydraulic pressure acting on the gate. When the level of the water in the waterway is at a normal level, the hydraulic pressure exerted on the gate is lower than the resisting force of the spring in the hydraulic cylinder, so that the spring in the hydraulic cylinder forces the piston and hence the piston rod to extend upwardly holding the gate in an upright position. When the water level increases, the hydraulic pressure on the gate exceeds the resisting force of the spring forcing the piston rod against the spring thus opening the gate. This apparatus is completely impractical for the applications of the present invention described above.
The above patents describe water control systems particularly where large bodies of water are involved. As above indicated, none address the problems faced by both towns and individual homeowners who are often threatened by flood waters at various points about a house or other building, or around the perimeter of a given building subdivision. In addition, none of the above patents describes any type of liquid barrier apparatus which would be practical or useful in containing sudden, emergency spills, especially of hazardous liquids or chemicals. Thus, there remains a need for a liquid barrier system that responds immediately and automatically, without human assistance, and so responds to raise the barrier wall only when liquid, including flood waters, hazardous liquids or chemical spills, are of a volume which cannot be otherwise contained or drained away to avoid a flood or human hazard. In addition, there is a need for such a liquid barrier system that is useful for roadways threatened by flood water that is reliable, easy to use, install and reset to a below ground level position. The various aspects of the present invention collectively provide apparatus which when installed provides such an advantageous system.